Using metasearch to discover what you missing in search: Dogpile.com

Dogpile’s missing pieces tool, provides a handy graphical way to determine what websites appear or don’t appear in the top results page on three top search engines; Google, Yahoo! And Ask Jeeves. Missing pieces is a flash system where a searcher can enter a keyword phrase and search for websites on all three major search engines. The missing pieces circle displays all sites appearing within each search engine, but also represents which sites appear on all three, just two, or only one search engine. Missing pieces lets you compare and discover the websites you were missing from the other search engines. However, no guarantees the other missing sites will provide a better resource in providing the best result for your search.

Dogpile had commissioned a study with the University of Pittsburgh and the Pennsylvania State University to determine the amount of overlap or lack of overlap between each search engine in the study. The study determined there was only a 3% overlap for page one searches with 10,316 searches, 12% of returned results were shared by two search engines, and 85% of returned results were unique to one search engine.